The present invention relates to an ultrasonic cleaning device for applying an ultrasonic treatment to a processing target. More specifically, the present invention relates to (1) an ultrasonic cleaning device and method used in a fabrication process of a flat display panel such as a liquid crystal display element or a PDP (plasma display panel) or in a fabrication process of a semiconductor substrate, and (2) a resist-stripping device for stripping and removing a resist by utilizing ultrasonic, for example, a resist-stripping device for stripping and removing a photoresist used in photolithography and the like in a liquid crystal display device fabrication process.
A cleaning part of an ultrasonic cleaning device of a conventional single substrate dipping type, that is used in a fabrication process of a flat panel display such as a liquid crystal display element or a PDP or in a fabrication process of a semiconductor substrate is provided with a vibrating element having a vibrating plate or the like, in a lower part of a cleaning bath that reservoirs a cleaning liquid. By operating a stripping element in a state in which a cleaning target such as a substrate is dipped in the cleaning liquid, ultrasonic vibration is applied to the cleaning liquid, so that the cleaning target is subjected to the ultrasonic cleaning treatment.
The foregoing ultrasonic cleaning device, however, requires a large quantity of a cleaning liquid. Besides, since the cleaning liquid in the cleaning bath is replaced regularly at predetermined intervals, there is possibility that the cleaning of a target would be insufficient. Furthermore, upon the cleaning treatment, transport of a target has to be suspended while the target is dipped into the cleaning liquid, thereby causing a longer time to be spent for the treatment.
On the other hand, the cleaning part of the ultrasonic cleaning device of a conventional single substrate type in which a cleaning liquid is supplied to a cleaning target by means of an ultrasonic cleaning nozzle is provided with an ultrasonic cleaning nozzle 102, above a substrate 101 that is the cleaning target, as shown in FIG. 10. A cleaning liquid (pure water, in the most cases) 103 to which ultrasonic has been projected (applied) is sprayed over an upper surface of the substrate 101, which is transported while being horizontally kept. In so doing, particles of organic materials, metallic materials, etc. adhering to the substrate 101 are removed, so that the surface is cleaned. Besides, the vibrating element for generating the ultrasonic to be projected to the cleaning liquid is usually provided inside the ultrasonic cleaning nozzle 102, or occasionally in a cleaning-liquid-supply pipe that connects the ultrasonic cleaning nozzle 102 with a cleaning-liquid-supply pump provided on an upstream side to the ultrasonic cleaning nozzle 102.
Usually applied as a method for spraying the cleaning liquid 103 is a showering method in which the cleaning liquid 103 is sprayed in a shower form with a width equal to or broader than that of the substrate 101 while ultrasonic is projected to the cleaning liquid 103 by the vibrating element.
According to the foregoing arrangement, the cleaning treatment of the substrate 101 is carried out always with the fresh cleaning liquid 103 (in the case where the cleaning liquid 103 is not collected and reused). Besides, the cleaning treatment to the substrate 101 can be carried out while the substrate 101 is being transported by transport rollers (not show) or the like.
Incidentally, the foregoing vibrating element is damaged or broken within a short period of time due to heat unless it is operated in a liquid having no bubbles. Therefore, when generating the ultrasonic, the vibrating element need be sufficiently surrounded by a liquid such as the cleaning liquid 103.
The aforementioned conventional ultrasonic cleaning device, however, has a nozzle opening 102a facing downwards above the substrate 101 as the cleaning target, and is arranged so that the cleaning liquid 103 is jetted downwards through the nozzle opening 102a. Therefore, bubbles likely intrude therein through the nozzle opening 102a. Besides, the distribution path of the cleaning liquid 103 (more specifically, the ultrasonic cleaning nozzle 102, the cleaning-liquid-supply pipe, the cleaning-liquid-supply pump, etc.) extends downwards or diagonally downwards, and bubbles generated upon operation of the vibrating element provided in the distribution path (more specifically, inside the ultrasonic cleaning nozzle 102) tend to remain therearound. Moreover, the bubbles having intruded therein are hardly discharged to outside the distribution path of the cleaning liquid 103.
Therefore, to flow the cleaning liquid 103 so as to prevent bubbles from remaining around the vibrating element, a complex structure is required, which is characterized as follows, for instance: (1) a plurality of cleaning liquid distribution paths are provided inside the ultrasonic cleaning nozzle 102; and (2) the inside wall of the ultrasonic cleaning nozzle 102 is formed in a tapered shape. Besides, to discharge bubbles through the nozzle opening 102a, it is necessary to flow a great quantity of the cleaning liquid 103 at all times, with the opening area of the nozzle opening 102a and the like taken into consideration. These problems have become severer as the substrate (cleaning target: processing target) 101 becomes larger in size. Furthermore, in the case of the above-described conventional ultrasonic cleaning device, to clean both the surfaces of the substrate 101 simultaneously is impossible, although to flow a great quantity of the cleaning liquid 103 is required.
Besides, the resist stripping treatment for stripping the resist applied on the substrate is either (1) a batch type in which a plurality of substrates are simultaneously subjected to the resist stripping treatment, or (2) a single substrate type in which the substrates are subjected to the resist stripping treatment one by one. The batch type, processing a plurality of substrates simultaneously, has an advantage of a higher processing capacity. As the substrate treated becomes larger in size, however, a quantity of an organic solvent or the like reservoired as a resist stripper in a stripping treatment bath increases. Thus, there are also problems regarding safety.
On the other hand, methods for the resist stripping treatment of the single substrate type include, generally, (1) a dipping method in which a substrate is dipped in a stripping treatment bath reservoiring a resist stripper, (2) a showering method in which a resist-applied surface of a substrate is sprayed with a resist stripper, and (3) a method in which the methods of the foregoing two types are used in combination. In some arrangements for the dipping method, an ultrasonic vibrating plate is provided at the bottom of the stripping treatment bath.
The single-substrate-type method is advantageous, particularly for a large substrate with a diagonal of not less than 1 m, in that a quantity of an organic solvent used is smaller as compared with that in the case of the foregoing batch type since the substrates are treated one by one. The time spent in the resist stripping treatment, however, becomes a rate-limiting factor, and therefore, the processing capacity of the single-substrate-type method is generally smaller than that of the batch-type method.
To improve the processing capacity of a device of the single substrate type, a processing chamber for stripping resist (stripping section) may be designed long, for example. Designing the processing chamber long, however, leads to problems of causing a device footprint larger and of increasing an organic solvent used, thereby impairing the advantage of the single substrate type. In the case of an arrangement for the dipping method, an ultrasonic vibrating plate is provided at the bottom of a stripping treatment bath, improvement of the resist stripping performance by utilizing the ultrasonic vibration is expected, but similar problems such as an increase in usage of an organic solvent arise since substrates to be processed are required to be dipped in the stripping treatment bath.
Any one of the foregoing methods (1) through (3) of the single substrate type is a method recycling and re-using the resist stripper, and requires provision of a circulation-use tank capable of reservoiring a certain quantity of a resist stripper (organic solvent), though the quantity is smaller than that in the case of the batch type. Therefore, this leads to problems such as spatial loss, and an increase in possibility of danger.
Regarding the single-substrate-type resist-stripping device, to improve a rate of the resist stripping treatment without damaging a resist-applied matter to make the device footprint and the length of the stripping section (device length) as small as possible is a task relevant to effective usage of a clean room space and indispensable for reducing the device costs. Besides, reduction of usage of a resist stripper, typically an organic solvent, closely relates not only to reduction of costs of raw materials and costs for processing a waste fluid, but also to solution of environmental problems such as reduction of a total amount of industrial waste, and it is therefore an important task that must be accomplished by the industrial world in the near future.
The present invention was made to solve the foregoing problems, and the object of the present invention is to provide an ultrasonic cleaning device ensuring stable operation of a vibrating element for generating ultrasonic without a complex structure and distribution of a great quantity of a cleaning liquid, thereby allowing device costs and device running costs to decrease.
To achieve the foregoing object, an ultrasonic cleaning device in accordance with the present invention is arranged so as to include an ultrasonic cleaning section having cleaning-liquid-supply means for supplying an ultrasonic-applied cleaning liquid to a cleaning target through a cleaning-liquid-supply opening, wherein (1) the ultrasonic cleaning section includes a vibrating element for generating ultrasonic in a cleaning liquid distribution path, at a position on an upstream side to the cleaning-liquid-supply opening, and (2) a part of the cleaning liquid distribution path immediately on a downstream side to the vibrating element extends from an upstream side to a downstream side in a direction in a range of a horizontal direction to an upward direction.
According to the foregoing arrangement, the part of the cleaning liquid distribution path positioned immediately on the downstream side to the vibrating element extends in a direction in a range of the diagonally upward direction to the upward direction. Therefore, bubbles generated upon operation of the vibrating element are easily discharged onto the downstream side of the distribution path along the flow of the cleaning liquid. Besides, bubbles intruding through the cleaning-liquid-supply opening or bubbles once discharged on the downstream side of the distribution path do not intrude in the vicinity of the vibrating element.
Therefore, a quantity of the cleaning liquid needed to discharge the bubbles in the vicinity of the vibrating element onto the downstream side of the distribution path can be drastically decreased. Additionally, a specific device for preventing bubbles from remaining in the vicinity of the vibrating element need not be provided, thereby ensuring remarkable simplification of the structure of the ultrasonic cleaning device.
Another object of the present invention is to provide a cleaning method enabling to clean upper and lower surfaces of a cleaning target more easily.
To achieve the foregoing object, a cleaning method in accordance with the present invention is a method including the steps of (1) supplying an upper surface cleaning liquid to an upper surface of a cleaning target, and (2) supplying an ultrasonic-applied cleaning liquid to a lower surface of the cleaning target supplied with the upper surface cleaning liquid.
According to the foregoing method, the ultrasonic-applied cleaning liquid is supplied to the lower surface of the cleaning target in a state in which a layer of the upper surface cleaning liquid is formed on the upper surface of the cleaning target. The vibration transmitted to the lower surface of the cleaning target is further transmitted to the upper surface side without attenuation, thereby ensuring that not only particles adhering to the lower surface but also those adhering to the upper surface can be simultaneously removed by means of the cleaning liquid and the ultrasonic. In short, an effect is achieved that a cleaning method capable of easily cleaning both the upper and lower surfaces of the cleaning target.
Still another object of the present invention is to provide a single-substrate-type resist-stripping device that is capable of carrying out a resist-stripping treatment at a high rate without damaging a resist-applied matter and that has a shorter device length and a smaller footprint.
To achieve the foregoing object, the resist-stripping device in accordance with the present invention is arranged so as to include a stripping section, wherein the stripping section includes (1) stripper-supply means for supplying a resist stripper to a resist-applied surface of a resist-applied matter, the resist stripper stripping a resist on the resist-applied surface, and (2) liquid-supply means for supplying an ultrasonic-applied liquid to a back surface opposite to the resist-applied surface supplied with the resist stripper.
According to the foregoing arrangement, the resist stripper is supplied to the resist-applied surface by the stripper-supply means. Subsequently, the ultrasonic-applied liquid is supplied by the liquid-supply means to the back surface opposite to the resist-applied surface. The ultrasonic vibration transmitted to the back surface is further transmitted to the resist stripper on the resist-applied surface via the inside of the resist-applied matter. Consequently, the stripping of the resist from the resist-applied surface and the dissolution of the resist into the stripper is promoted, resulting in drastic reduction of the time required for the resist stripping treatment (the processing performance can be drastically improved). Besides, usage of the resist stripper can be reduced. As a result, the resist-stripping device can be made shorter in length, the footprint thereof can be made smaller, and the usage of the resist stripper can be reduced.
Furthermore, since the ultrasonic vibration is indirectly transmitted to the resist-applied surface side, another effect can be achieved that only the resist can be stripped without damaging the structure (circuit patterns, etc.) formed on the resist-applied surface, as compared with the case where the ultrasonic vibration is applied directly to the resist-applied surface side.
For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.